The present invention relates to a bobbin holder device for coiling and feeding thread.
A conventional bobbin holder device is constructed as shown in cross-section in FIG. 1. In FIG. 1, reference numeral 1 designates a driving motor; 11, a bearing in the motor; 3, a holder shaft; 31, a driving shaft; and 33, a middle shaft. The shafts are connected through shaft joints 32 and 32'. Reference numeral 2 designates a support body. A screw 34 is engaged with a nut 35 at the end of the shaft so that the shaft 3 and a bobbin holder body 4 are connected with each other. Reference numeral 36 designates a bearing; 37, a stop ring for the bearing; 5, a piston in the bobbin holder body 4; 51, an O-ring; 52, a cap covering the end of the holder body 4; 53, a spring; 54, a spacer; 55, a stop ring; 56, a screw at the end of the extending portion of the piston; 57, a nut; 42, a sleeve; 43, a bobbin holding member composed of an elastic ring; and 6, a bobbin.
In the thus-arranged conventional bobbin holder device, the nut 57 is screwed onto the screw 56 so that the cap 52 and the piston 5 are fixed to each other and pulled rightwardly in the drawing by the spring 53 to push the sleeve 42 rightwardly to thereby press this assembly against the bobbin holder body 4. The bobbin holding member 43 is pressed from opposite directions to expand outwardly to thus press against the bobbin 6 on the outside to thereby fix the bobbin 6 to the bobbin body 4. When the holder shaft 3 is driven by the motor 1, the bobbin holder body 4 fixed by the nut 35 rotates together with the shaft and the bobbin 6 rotates through the bobbin holding member 43 so as to perform, for example, thread coiling or feeding.
To remove or exchange the bobbin 6, pressurized air is supplied into the space 41 to force the piston 5 leftwardly in the drawing against the spring 53. The cap 52 also moves leftwardly, loosening the bobbin holding member 43, whereupon the bobbin 6 can be removed.
More specifically, pressurized air is fed from an air source (not shown) through an inlet hole 21 formed in the support body 2. The pressurized air enters a first chamber 26, flows through a passage 23 through a hole 22, and then enters the space 41 through a passage 23'. The passage 23 and a second chamber 27 between the bearings 36 and 36 are communicated with each other through a hole 22'. The piston 24 and a rubber ring 25 on the end of the piston 24 are provided for maintaining in airtight fit between the support body 2 and the rotating bobbin holder body 4. The piston 24 is pressed from the rear in the drawing so as to press against the rubber ring 25 to maintain the seal.
In such a conventional arrangement, although the first and second chambers should be at the same pressure, a pressure difference may occur due to a lack of a good seal. Because such a pressure difference can give rise to a flow from the outside containing dust, thread waste, or other contaminants, the service life of the bearing tends to be short. Also, such a flow can cause a loss of lubricant, further tending to shorten the bearing life.
In an attempt to alleviate these problems in the bobbin holder device, an arrangement as shown in FIG. 2 has been proposed. In FIG. 2, the bobbin portion has the same structure as that in FIG. 1, and the same reference numerals as those used in FIG. 1 designate the same parts. The two arrangements differ, however, in how pressurized air is fed to the space 41. The pressurized air in the case of FIG. 2 flows from right to left in the drawing through a hole 30 formed in each of the driving shaft 31, the middle shaft 33, and the holder shaft 3. In this case, it is necessary to conduct the pressurized air through the shaft joints 32 and 32'.
An object of the present invention is to provide a fluid coupling device in such a case where the fluid flows through passages formed through a pair of shafts with a fluid coupling device being provided to conduct the fluid between the shafts. More particularly, it is an object of the invention to provide a fluid coupling device for use in a thread bobbin holder device having a simple structure but which conducts fluid between two shafts in an airtight manner.